Vane construction for pneumatic device



y 9, 1970 s. K. SMQTH 3,512,908

VANE CONSTRUCTION FOR PNEUMATIC DEVICE Filed Sept. 16, 1968 FIG. 2

63 6| FIG. 48 FIG. 4A PRIOR ART IMPROVEMENT 55 4 l!AlI INVENTOR STANLEYK. SMITH ATTORNEY United States Patent O M VANE CONSTRUCTION FORPNEUMATIC DEVICE Stanley K. Smith, Baltimore, Md., assignor to The Blackand Decker Manufacturing Company, Towson, Md.,

a corporation of Maryland Filed Sept. 16, 1968, Ser. No. 760,013 Int.Cl. F04c 1/00; F01c 1/00; F04h 21/08 U.S. Cl. 418-179 1 Claim ABSTRACTOF THE DISCLOSURE The device disclosed herein is a portable, rotary-typefluid handling device, such as a pump, motor or the like, which includesa generally cylindrical casing having a rotor rotatably supportedtherein. One or more vanes are slidably carried by the rotor and duringrotation of the latter slide around the inner surface of the casing.Fluid inlet and outlet openings are formed in the casing for fluid entryand discharge during use of the device.

SUMMARY OF THE INVENTION The present invention deals specifically with anovel vane construction for use in and in combination with a rotary,fluid handling, pump, motor and the like. The vane is constructed of aformable, synthetic material and has embedded therein elongated fibersconstructed of graphite or alumina which extend in a directionlongitudinally of the vane. This construction contributes significantlyto the life and performance of the vanes and greatly enhances theelliciency of the overall device by increasing dimensional stability,reducing friction and extending tool life.

Main objects of the present invention, therefore, are to provide a novelrotor vane construction for use in and in combination with a fluidhandling device such as a pump, motor and the like, which constructionenhances vane life and efficiency of the device.

Further objects of the invention are to provide a vane construction ofthe above character which is relatively inexpensive to manufacture,rugged in construction and reliable in use.

Other objects and advantages of the invention will be come more apparentfrom a consideration of the detailed description to follow taken inconjunction with the drawings annexed hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view, partlybroken away, illustrating a fluid operated tool embodying the presentinvention;

FIG. 2 is an enlarged view of a portion of FIG. 1 and with the vanepartly broken away to illustrate one form of the invention;

FIG. 3 is an enlarged sectional view of a portion of FIG. 2 taken alongthe line 3-3 thereof;

FIG. 4A is an enlarged view of a portion of FIG. 2 and illustrating theclearance between moving and sta tionary parts made possible by thepresent invention;

FIG. 4B is a view similar to FIG. 4A and illustrating the necessaryclearance in some prior art constructions; and

FIG. 5 is a view similar to FIG. 3 illustrating a laminated vaneconstruction.

BROAD STATEMENT OF THE INVENTION Broadly described, the presentinvention relates to a fluid handling device including the combinationof a stationary cylinder having respective end plate means, a rotorrotatable within the cylinder axially between the end plate means, saidrotor having at least one radial slot formed therein, a vane freelymounted for radial sliding move- Patented May 19, 1970 ment in saidslot, whereby said vane has a longitudinal edge in sliding engagementwith the cylinder, said vane having generally parallel side edges ateither end of said longitudinal edge and spaced apart a distanceslightly less than said end plate means thereby defining clearancebetween said vane and end plate means; the improvement wherein said vaneis constructed of a synthetic formable material having superimposedlayers of woven cloth material embedded therein, said cloth materialincluding threads extending only in a direction generally parallel tosaid longitudinal edge and generally perpendicular to said side edgesand formed of a material selected from the group consisting of graphiteand alumina, said cloth material further including threads extending ina direction generally perpendicular to said longitudinal edge andgenerally parallel to said transverse edges and formed of a materialselected from the group consisting of wool, cotton, linen and mixturesthereof, rayon, nylon, Orlon and acrylic fibers, whereby said vane hasimproved dimensional stability in the longitudinal direction, wherebythe coefficient of friction of said longitudinal edge is minimized, andwhereby the longitudinal clearance with the respective end plate meansis minimized for reduced air consumption and improved motor efliciency.

In another aspect, the present invention relates to a vane for use in arotary fluid handling pump, motor and the like, said vane comprising anelongated flat member having a generally straight, longitudinal edge anda pair of generally straight, transverse edges, said member including abody of synthetic, fabricated material having elongated threads embeddedtherein, said threads including threads extending only in a directiongenerally parallel to said longitudinal edge and generally perpendicularto said transverse edges and constructed of a material selected rom thegroup consisting of graphite and alumina, whereby said vane has improveddimensional stability in the longitudinal direction and the coefficientof friction of said longitudinal edgeis minimized.

DETAILED DESCRIPTION Referring now specifically to the drawings, arotary, pneumatic power tool, which is one type of device to which thepresent invention applies, is illustrated generally at 11 in FIG. 1.However, it is to be understood that this is for purposes ofillustration only and that the present invention has application to thebroad class of fluid handling pumps, motors and the like and whetherthey be portable or stationary.

With this in mind, the tool 11 is seen to include a motor housing 13having a pistol-grip type handle 15 integral therewith or otherwisesuitably secured thereto. A pneumatic motor 17 is positioned within themotor housing 13 and is powered by compressed air supplied thereto froma source through a suitable inlet conduit 19 at the handle 15. Deliveryof compressed air to the motor 17 is controlled by conventional valving(not shown) located within the handle 15 and which, in turn, iscontrolled by a trigger 21 mounted on the handle 15. The details of thevalving (not shown) and the interrelation of the trigger 21 therewithhave been omitted here since they form no part of the present inventionand since they are well within the scope of the skilled engineer.

The illustrated pneumatic motor 17 is of the type having a hollow,stationary cylinder 23 secured within the motor housing 13 and with itslongitudinal, central axis extending longitudinally of the housing. Thecylinder 23 has a cylindrical, inner surface 25 and its fore and aftends are closed by end plates 27, 29 suitably secured thereto. A rotor31 is disposed within the cylinder 23 and between the end plates 27, 29and aligned stub shafts 33, 35 which extend through aligned openings 37,39 in the end plates 27, 29, respectively, and are journaled in suitablefashion,

for example, by bearings (not shown) carried by the end plates 27, 29.The axis of the stud shafts 33, 35 is radially offset relative to thelongitudinal axis of the cylinder 23 so that the rotor 31 rotateseccentrically relative to the axis of the cylinder 23.

The end plates 29, 27, or preferably the cylinder 23, are provided withsuitable inlet and discharge opening means (not shown) communicated withthe stator interior and with the valving (not shown) for the deliveryand discharge of compressed air to and from the motor 17 Again, thisconstruction is not illustrated nor described further here since itforms no part of the present invention and since it is fully within therealm of the skilled engineer.

The rotor 31 is formed with one or more radial slots 41 which extend thefull axial length of the rotor 31 between the end plates 27, 29. Asshown in FIG. 2, the slots 41 may be concavely curved along their radialinward end 43 while the end plates 27, 29 have straight, generallyradially extending faces 45, 47, respectively, which define the lateralends of the slots 41. A vane 49 is disposed within each of the rotorslots 41 and is adapted to slide radially thereof during rotor rotation.The vanes 49 (if more than one is used) are identical and each includesan elongated, flat body having a longitudinal, straight edge 51 adaptedto ride around the cylinder surface and bounded by parallel, straight,lateral side edges 53, 55 which are slidable adjacent the end platesurfaces 45, 47, respectively. An inner, generally convex edge 57 oneach vane 49 is generally complementary to and disposed opposite theassociated slot inner end 43.

During use, compressed air is admitted to the cylinder 23 and bearsagainst the vane or vanes 49 causing the rotor 31 to turn about the axisof the stub shafts 33, while centrifugal force causes the vane or vanes49 to slide radially outwardly in their respective slots 41. This, inturn, causes the longitudinal edge 51 of each vane 49 to remain insliding contact with the cylinder surface 25. The side edges 53, of eachvane 49 are spaced apart a distance equal to the vane length and thisdimension is selected to provide a predetermined clearance relative tothe end plate surfaces 45, 47.

Many prior art vanes are constructed using laminated plastic materialsselected from that group which has good shock and wear resistance aswell as low moisture absorption characteristics. These vanes alsogenerally employ a woven cloth constructed of organic or syntheticfibrous yarn, such as, for example, linen, cotton, wool or mixturesthereof, nylon, rayon, Orlon or acrylic material embedded in one or morelayers of the laminated plastic to enhance its shock, and wearresistance together with its resistance to fracture.

These organic or synthetic fiber cloth reinforced vanes, however, havethe detracting feature of being somewhat dimensionally unstable becauseof the moisture absorbing characteristics of these fibrous cloths. Thus,moisture in the device (either the fluid itself or moisture carriedthereby) causes the cloth fibers and the vanes to elongate in thedirection of fiber length. In the radial or transverse direction, thiselongation may not be objectionable. However, the expectation of vaneelongation in the axial or longitudinal direction requires thatsufficient clearance be provided between the end plate faces 45, 47 andthe vane edges 53, 55 to prevent the vanes 49 from hanging up duringmotor operation. It will be appreciated then that under conditions whenthe vane reinforcing fibers are less than saturated, excess clearanceexists between the vane edges 53, 5S and end plate faces 45, 47 and thepower and efficiency of the device is impaired.

In an effort to overcome this problem, a novel vane constructiondisclosed in the copending application of William S. Brucker, Ser. No.575,887, filed Aug. 29, 1966, now Pat. No. 3,417,664, issued Dec. 24,1968, and owned by the assignee of the present application has beendeveloped. There, a vane construction embodying reinforcing threadsextending in a direction longitudinally of the vane and formed of arelatively hard material having low moisture absorbing and lowcoefficient of friction properties, e.g., glass fiber, was disclosed.This novel vane construction provides the desired dimensional stabilitycharacteristics so that with this vane, clearance between the vane edges53, 55 and the end plate faces 45, 47 is minimized.

In addition, some of these longitudinally extending threads becomeexposed at the vane edge 51 as the synthetic vane material wears away.Thus, these threads (e.g. glass fiber) facilitate higher rotor speedsand increased output for the reason of the low coefficient of frictionprovided by these threads and because this relatively hard materialpolishes the cylinder surface 25 reducing its coefficient of frictionand pressure losses therepast. Furthermore, the lower friction achievedby this construction produces less heat in the device and increases theexpected vane life. All in all, the invention disclosed in the Bruckerapplication has made a significant contribution to the field of rotary,vane-type fluid handling devices.

In the present application, a similarly formed vane embodying a body ofsynthetic, fabricated material having reinforcing threads constructedfrom a material selected frm the group consisting of alumina andgraphite is disclosed. Thus, it has been discovered that a vanereinforced with alumina or graphite threads embedded therein andextending in a longitudinal direction possesses highly desirabledimensional stability and low friction characteristics. In addition,these longitudinally extending, alumina or graphite threads polish thecylinder surface 25 during use and enhance the efficiency and reduce thelosses of the device in which it is used.

Thus, as shown in FIGS. 2 and 3, the vane 49 comprises an elongated bodyof synthetic, fabricated material having embedded therein reinforcingthreads 59 constructed of alumina or graphite which extend in an axialor longitudinal direction. For ease of fabrication, these threads 59 areinterwoven in cloth-like fashion with other threads 61 which extendradially or transversely of the vane 49. Desirably, these threads 61 arerelatively soft, so as not to gouge the cylinder wall 25, and aremoisture absorbing so that the synthetic, fabricated vane material willadhere thereto. A material selected from the group consisting of linen,cotton, wool and mixtures thereof, nylon, rayon, Orlon and acrylicfibers is satisfactory for these threads 61 even though these materialswill expand with moisture absorption since radial elongation of the vane49 may not be objectionable.

It will be appreciated that the woven cloth embedded in the vane bodyincreases the resistance of the vane to shear or fracture under shockloading. The longitudinal threads 59 are substantially non-moistureabsorbing while the transverse threads 61 are highly moisture absorbent.This makes the vane strength greater in planes parallel to thelongitudinal edge 51 than in p anes perpendicular thereto. However, theprimary shock loads on the vane 49 occur when the vanes rock in anarcuate direction within their slots 41 and are thrown against the outerradial edges of the slots 41. These loads develop stresses in planesparallel to the edge 51 which is the direction in which the vanes 49'have their greatest strength.

It will be appreciated that in some cases it may be desirable to providegreater strength in the vane along planes normal to the vane edge 51. Inthese cases, it may be possible to substitute threads made of materialselected from the group described above for threads 61 for some of thelongitudinal alumina or graphite threads 59. The substituted threads aremore absorbent and provide a stronger bond to the synthetic fabricatedvane material thereby increasing the strength of the vane along planesrunning transverse thereto. The remaining alumina or graphite threads 59are substantially non-absorbent and therefore provide greaterdimensional stability than would be attained without them. In addition,the remaining alumina or graphite threads 59 also contribute to loweringthe coefficient of friction and increasing the hardness of the vane edge51 as these threads become exposed along this edge.

The vane construction disclosed is readily formed using known andconventional manufacturing techniques. Thus, for example, the threads59, 61 may be woven, using known weaving techniques, and passed througha bath of the synthetic, formable vane material in liquid form. Thenon-absorbent threads 59 are coated with this material while the threads61 are impregnated thereby and the treated cloth is then passed throughcalender-type rolls which apply a relatively thick layer of thesynthetic material, e.g., thermosetting resin, thereto. The resultingproduct, shown in FIG. 3, may then be dried but is not allowed to set.Thereafter, one, or if desired, several superimposed layers of thismaterial are placed in a hydraulic press and are heated to the finalcuring temperature of the synthetic material. If a plurality ofsuperimposed sheets are molded, a construction such as that shown at 63in FIG. is formed. In either case, the formed sheet can then be cut tosize employing known techniques to form the vanes 49. In the event onlythe longitudinal threads 59 are employed, they are treated and coated inthe same way except that a different mechanism, adapted to handle theseunwoven threads, need be employed.

With reference now to FIGS. 4A and 4B, a comparison between the requiredinitial axial or longitudinal clearance between the rotor vanetransverse edge 55 and the end plate surface 47 of the present inventionand that of the prior art is illustrated. In vanes using longitudinalthreads constructed or moisture absorbing material such as linen,cotton, wool or mixtures thereof, nylon, Orlon, rayon or acrylic fibers,an initial clearance which is a function of the vane length and thecoefficient of expansion of the particular longitudinal thread, fibermaterial. This initial clearance is represented at B in FIG. 4B. In thepresent invention where the longitudinal threads 59 are constructed fromalumina or graphite, an initial clearance represented at A in FIG. 4A isrequired which substantially is only that clearance necessary to preventexcessive friction between the vane 49 and the end plate faces 45, 47.In the prior art constructions described, a clearance A was reached onlywhen the longitudinal fibers were substantially completed saturated sothat prior to this saturated condition, sub stantial power losses weresustained.

By the foregoing, there has been disclosed a novel vane constructioncalculated to fulfill the inventive objects hereinabove set forth, andwhile a preferred embodiment of the present invention has beenillustrated and described in detail, various additions, substitutions,modifications and omissions may be made thereto without departing fromthe spirit of the invention as encompassed by the appended claim.

I claim:

1. In a fluid handling device including the combination of a. stationarycylinder having respective end plate means, a rotor rotatable within thecylinder axially between the end plate means, said rotor having at leastone radial slot formed therein, a vane freely mounted for radial;sliding movement in said slot, whereby said vane has a longitudinal edgein sliding engagement with said cylinder, said vane having generallyparallel side edges at either end of said longitudinal edge and spacedapart a distance slightly less than said end plate means therebydefining clearance between said vane and end plate means; theimprovement wherein said vane is constructed of synthetic formablematerial having superimposed layers of woven cloth material embeddedtherein, said cloth material including threads extending only in adirection generally parallel to said longitudinal edge and generallyperpendicular to said side edges and formed of a material selected fromthe group consisting of graphite and alumina, said cloth materialfurther including threads extending a direction generally perepndicularto said longitudinal edge and generally parallel to said transverseedges and formed of a material selected from the group consisting ofwool, cotton, linen and mixtures thereof, rayon, nylon, Orlon andacrylic fibers, whereby said vane has improved dimensional stability inthe longitudinal direction, whereby the coefficient of friction of saidlongitudinal edge is minimized, and whereby the longitudinal clearancewith the respective end plate means is minimized for reduced airconsumption and improved motor efficiency.

References Cited UNITED STATES PATENTS 3,107,152 10/1963 Ford et al 3083,116,975 1/1964 Cross at al. 3,151,015 9/1964 Griffith 308-2383,417,664 12/1966 Brucker 103-216 HENRY F. RADUAZO, Primary Examiner US.Cl. X.R.

